Osuk Y. Kwon

Rough surface interferometry at 10.6 μm

An IR Twyman-Green interferometer is described. It uses a cw CO(2) laser as a light source operating at a 10.6-microm wavelength. Theoretical analysis and experimental measurements of the relationship between the contrast of the interference fringes and the rms roughness of test surfaces are discussed. Interferometric testing results and special alignment methods are shown for rough surface optics.

Infrared point-diffraction interferometer

A point-diffraction interferometer (PDI) for use in the infrared is discussed. It is shown that the PDI is simple and easy to use and also yields fringes of constant optical path difference similar to those obtained with a Twyman–Green interferometer. The fabrication of the PDI is described, and typical results obtained using the interferometer at a wavelength of 10.6 μm are shown.

Full Aperture Testing With Subaperture Test Optics

This paper is an overview of recent work of the Lockheed Palo Alto Research Laboratory on the use of subaperture test optics to evaluate the performance of large optical systems. Supported by selected subscale experiments, a theory has been developed that addresses two test conditions, each based on the use of a known test flat in a double-pass configuration with a collimated optical system of unknown quality. The two test conditions, in order of increasing theoretical complexity, are: (1) a single test flat covering only a portion of the full-system aperture, and (2) multiple (not necessarily coherent) test flats. Analyses predict limited utility of a single test subaperture as a function of a subaperture size and location, and aberration content. Multiple subapertures viewing the full system are shown to give good results for higher order aberrations even when the individual test flats are unphased and contain large relative tilt errors. The test techniques described here are fully scalable to future optical systems of arbitrary size. This paper summarizes the theoretical basis for subaperture testing, gives quantitative performance predictions for some selected cases, and presents the results of supporting experimental work.

Infrared scatterplate interferometry.

Scatterplate inferferometry in the IR (lambda = 10.6 microm) is virtually the same as that in the visible except for an appropriate change in optical materials. Techniques for its fabrication and alignment are described. Some of the side effects produced by the pyroelectric vidicon that are peculiar to scatterplate interferometry are discussed.

10.6 Micrometer Interferometric Testing Of Infrared Optical Components And Aspherics

Infrared interferometric systems using a CO2 laser operating at a wavelength of 10.6 μm are described. Specific systems discussed are a Twyman-Green interferometer and a Twyman-Green interferometer with an infrared computer-generated hologram (IRCGH). The reduced sensitivity due to the longer wavelength enables us to test optical components necessary for IP high-energy laser systems. This paper also illustrates typical results obtained from testing infrared trans litting materials, diamond-turned metal mirrors, and aspherics. Special alignment techniques and basic limitations of infrared interferometry are discussed.

Long-Wavelength Interferometer In The Optical Shop

The in situ testing of an unpolished off-axis parabolic mirror with a vertex radius of 12.8 m, a diameter of 1.42 m, and an off-set of 1 m is described. Interferograms are shown that were obtained during the fabrication process by means of a lona-wavelength interferometer that uses a CW CO2 laser operating at a wavelength of 10.6 µm as the coherent light source.